Final answer:
Nonionizing radiation is the least energetic type of radiation listed, with low energy that typically transfers as heat without ionizing molecules. so, option D is the correct answer.
Step-by-step explanation:
The least energetic type of radiation among the options provided is Nonionizing radiation. Nonionizing radiation, which includes light and microwaves, is relatively low in energy and is typically used as a heat source. In contrast to ionizing radiation, such as alpha (α) particles, beta (β) particles, gamma (γ) rays, X-rays, and high-energy ultraviolet radiation, nonionizing radiation does not have enough energy to knock electrons out of molecules. Alpha particles have a relatively short range and can't penetrate far into material, beta particles have a greater penetrating ability, and gamma rays are the most penetrating.
However, when considering the actual energy levels, nonionizing radiation is the least energetic as it does not cause ionization and typically results in the transfer of energy in the form of heat rather than causing damage to biological tissues.
In contrast, beta particles (B) and gamma rays (y) have higher energies and can penetrate matter to a greater extent compared to alpha particles. Beta particles are negatively charged electrons or positively charged positrons. Gamma rays are electromagnetic waves with the highest energy and can penetrate the farthest into matter.